In recent years, the Thin Film Transistor-LCD (TFT-LCD) has been rapidly developed and applied widely. Most of the liquid crystal displays on the present market are back light type liquid crystal display devices, which comprise a liquid crystal display panel and a back light module. Generally, the liquid crystal display panel comprises a CF (Color Filter) substrate, a TFT (Thin Film Transistor) substrate, LC (Liquid Crystal) sandwiched between the CF substrate and TFT substrate and sealant. The working principle is that the light of backlight module is reflected to generate images by applying driving voltages to the two glass substrate for controlling the rotations of the liquid crystal molecules.
For the TFT-LCD in the mainstream market, three types, which respectively are Twisted Nematic (TN), Super Twisted Nematic (STN), In-Plane Switching (IPS) and Vertical Alignment (VA) can be illustrated. The VA liquid crystal display possesses extremely high contrast than the liquid crystal displays of other types. It has very wide application in large scale display, such as television or etc. The High Vertical Alignment (HVA) mode is one important branch in the VA modes. When the HVA liquid crystal display panel functions, the twist of the liquid crystal molecules in the liquid crystal layer is controlled by the vertical electric field formed by the pixel electrode of the array substrate side and the common electrode of the color filter substrate side.
Generally, a black matrix is provided at one side of the TFT substrate facing the CF substrate. As shown in FIG. 1, the liquid crystal display panel comprises an upper substrate 100, a lower substrate 200 and a liquid crystal layer 300 located between the upper substrate 100 and the lower substrate 200, and the upper substrate 100 comprises a first substrate 110, a black matrix 120 located on the first substrate 110, a color filter layer and a common electrode layer 140, wherein the color filter layer comprises a red color block 131, a green color block 132 and a blue color block; the lower substrate comprises a second substrate 210, gate scan lines and data lines 220 located on the second substrate 210, a passivation layer 230 and a pixel electrode layer on the passivation layer 230, wherein the gate scan lines and the data lines 220 surround to form a plurality of sub pixel areas, and the pixel electrode layer comprises one pixel electrode 240 correspondingly in each sub pixel area, and the pixel electrode 240 is divided into a plurality of regions in each sub pixel, such as a pozidriv shape pixel electrode, and the common electrode layer 140 is a continuous plane type common electrode; the red color block 131, the green color block 132 and the blue color block are located respectively corresponding to the sub pixel areas.
In the development of the liquid crystal display technology, it is a trend of the technology development that the black matrix of the CF substrate side is removed either for the consideration of saving the cot or the consideration of the curve design. However, the display quality issue happens if there is no black matrix. As shown in FIG. 2, the liquid crystal panel does not comprise the black matrix. In the condition of black state, the voltage levels of the pixel electrode 240 and the common electrode 140 are the same, no light leakage occurs in the sub pixels. However, in condition that the voltage of the data line 220 and the voltage of the common electrode 140 are not the same, an electric field may generate to drive the liquid crystals to be twisted and cause the light leakage; as shown in FIG. 3, the liquid crystals 300 are twisted because of being driven by the electric field formed by the data line 220 and the common electrode 140. Accordingly, the border light leakage phenomenon of the sub pixel areas happens. Besides, while the alignment of the TFT substrate and the CF substrate is shifted and the liquid crystal panel does not comprise the black matrix, the color washout issue can easily occur. As shown in FIG. 4, while the alignment of the CF substrate 100 and the TFT substrate 200 is shifted, and the pixel electrode 240 previously drives the liquid crystals in the green sub pixel to show the green image, due to the alignment shift, the electric field of the pixel electrode 240 may have chance to influence the liquid crystals at the border of the red sub pixel and result in that the green image is mixed with a little red color and the color washout happens. Similarly, the same situation will also happen at the gate scan line position of the liquid crystal panel.